1. Field
A centrifugal fan and an air conditioner using the same are disclosed herein.
2. Background
FIG. 1 shows a centrifugal fan used in a general air conditioner. The centrifugal fan 10, used in, for example, an indoor unit or device of an air conditioner, may include a hub 11, a plurality of blades 12, and a shroud 13.
As shown in FIG. 1, as the hub 11 having the plurality of blades 12 is rotated at a high speed in a counterclockwise (P) direction by a rotational force of a motor, a fluid that has been sucked through a central hole provided in or at an upper side of the shroud 13 is discharged to a side surface N by the plurality of blades 12 formed in the hub 11. However, a wing tip vortex S is generated at an upper side of the blade 12, as shown in FIGS. 2A-2B, thus causing noise and aerodynamic loss. An air flow W, which is opposite perpendicular to a direction of discharge is exerted to a right side of the blade 12, so that noise is unnecessarily increased and efficiency of the fan deteriorated.
Centrifugal fans having a novel structure have been suggested to address such issues. As shown in FIG. 3, centrifugal fan 20 disclosed in Korean Patent Application Publication No. 2005-0119071 has a structure in which a plurality of blades 22 are formed in or on a hub 21 without a shroud.
A side of each of the plurality of blades 22 is formed by injection molding to have a stereoscopic shape 22a of a twist similar to an S shape, as shown in FIGS. 4A-4B, and thus, an upper side and a bottom side of each of the plurality of blades 22 has a step having a predetermined distance D with respect to a vertical direction.
The upper side of the blade 22, as shown in FIGS. 4A-4B, has a gentle wing tip 22b with an area increasing towards its outer circumferential portion from its inner portion with respect to a middle portion of the hub 21. Accordingly, the gentle wing tip 22b may pull a generated wing tip vortex S thereby keeping the wing tip vortex S constant. The gentle wing tip 22b may also send the fluid in an opposite direction of the hub 21 to thereby accelerate the flow of the fluid. The detailed description is disclosed in Korean Patent Application Publication No. 2005-0119071.
However, in order to inject-mold the plurality of blades 22 provided on the hub 21 so that the plurality of blades 22 have a twisted stereoscopic shape 22a similar to the S shape, a highly sophisticated injection molding technology is required, thus increasing fabrication costs. Moreover, in a case that the stereoscopic blades 22 with the above-described gentle wing tips 22b formed at upper sides thereof are individually injection-molded and formed on the hub 21, working efficiency may be extremely deteriorated in light of productivity.